1. Field of the Invention
This invention relates to novel disazo reactive dyestuffs for cellulose fibers.
2. Description of the Prior Art
Heretofore, when dyeing a cellulose fiber, there has been employed a method which comprises effecting dyeing by using a reactive dyestuff in the presence of an acid-binding agent such as sodium carbonate, potassium carbonate, sodium hydroxide etc. and an electrolyte such as sodium chloride, sodium sulfate etc. at a pH of 10 or more and a temperature of not higher than 100.degree. C.
However, in recent years, there has been an increasing demand for mixed spun cloths composed of cellulose fibers and other fibers, especially polyester fibers, and in order to dye such cellulose/polyester mixed fibers (hereinafter referred to as C/P fibers), it has been necessary to employ appropriate dyestuff and dyeing conditions for the cellulose fiber and also appropriate dyestuff and dyeing conditions for the polyester fiber respectively. It is because the dyestuff and dyeing conditions for dyeing the polyester fiber greatly differed from those for the cellulose fiber. In other words, it is because, in order to dye the polyester fiber, it was necessary to use a disperse dyestuff and dye at a temperature of about 130.degree. C.
For example, when attempting to dye the aforesaid C/P fiber in the same step, it involves dyeing by using two different dyestuffs from a combination of a reactive dyestuff and a disperse dyestuff, and thus there are several problems. For example, in order to adequately fix the reactive dyestuff to the cellulose fiber, it is necessary to raise the pH to 10 or higher with an acid-binding agent, but the presence of the acid-binding agent promotes the decomposition of the disperse dyestuff and thus the fixation of the disperse dyestuff to the polyester fiber is inadequate. On the other hand, in order to fix the disperse dyestuff to the polyester fiber, high temperature conditions (generally 130.degree. C.) are required, but, under such high temperature conditions under the aforesaid high pH conditions, the hydrolysis of the reactive dyestuff is greatly promoted, and thus the fixation of the dyestuff to the cellulose fiber is greatly inhibited. Therefore, where such a C/P fiber is to be dyed, it has been a common practice to employ a two-bath method which comprises dyeing first either of the cellulose or polyester fiber and subsequently dyeing the other thereof in a separate bath.
Therefore, it is an object of this invention to provide disazo dyestuffs for cellulose fibers which can dye a cellulose fiber under pH and dyeing conditions for dyeing a polyester fiber with a disperse dyestuff.